I wasn’t aware of the London one, but the solution used outside Cardiff must be a way forward to reduce the cost of further electrification by eliminating the need to demolish very difficult bridges.
Like so many things the answer is probably "it depends". When the Filton Bank electrification was being developed the solution now adopted in Cardiff didn't exist, so probably nobody considered it as an option. If the scheme now went ahead then I imagine someone would investigate whether it was possible at all on this site, and if so whether it was cheaper than any of the other options.
The Cardiff option was to use novel insulating paint, allowing them to stick the contact wires right up against the bridge. They've lowered track where that was possible lots of times
I think you’ve misinterpreted edwin_m’s post. He wasn’t suggesting track lowering wasn’t possible AFAICS...
Might be able to slightly hump the actual bridge to give a bit more room over the wires?
That would not be very good 'future proofing'. One can easily foresee local services becoming bi-mode and also XC services plus regional ones too.
Only the Earth Wire remains uinstalled over the P4 track.
Can confirm that’s the case with only the return/earth wire only to install.
Just read the twitter thread. Thanks - very interesting - well worth the time spent reading it.
Noel Dolphyn of F & F seemed to be implying that the tunnel section under the river was working /energised, but just needed testing - is that not so??
AIUI, it’s still supplied along the line of route from one of only two possible grid supply sources, either primarily from near Cardiff, or alternatively from Thingley Jn, near Melksham. To me, shortening the distance between sectioning switchgear doesn’t necessarily make an area ‘stand alone’, electrically speaking. Wouldn’t a Significant tunnel installation normally be capable of isolation at either end anyway?
That would be my understanding. In other words it can only be isolated on a ‘stand alone’ basis...